Lisa Willis left Philpott 10 years after she moved into the home he shared with his wife and their children, the court heard.
She had four of her own children with Philpott during that time and said she and his wife Mairead took it in turns to alternate nights to share a bed with him.
Philpott, 56, his 31-year-old wife and a third defendant, 46-year-old Paul Mosley, are on trial for the manslaughter of the Philpotts’ six children.
Jade, 10, and her brothers John, nine, Jack, eight, Jesse, six, Jayden, five, and Duwayne, 13, all perished after a fire which engulfed their home in Victory Road, Allenton, Derby, as they slept in their beds in the early hours of May 11 last year.
All three defendants have denied the charges.
The family achieved notoriety in 2006 and 2007 when they appeared on the Jeremy Kyle Show and in a documentary with MP Ann Widdecombe.
Giving evidence from behind a screen at Nottingham Crown Court, Miss Willis, 29, agreed with Philpott’s barrister, Anthony Orchard QC, that the result was unpleasant.
“Mr Philpott was being lambasted as a benefits scrounger. You were seen as a shameless family. It was a horrible time, wasn’t it?”
“Yes it was,” Miss Willis said.
He went on: “Michael Philpott is a man who raises in people quite a lot of emotion. People either love him or hate him.
“He could be arrogant. He could be a bit of a loudmouth. He would shout his business to anyone who would listen. He could rub people up the wrong way.
“There are some people who like him but many who do not.” Miss Willis replied: “Yes, that’s true.”
The prosecution case, which was opened Monday by Richard Latham QC, alleges the Philpotts and Mosley started the fire in a botched plan to set up Miss Willis after she and her five children, four of whom were fathered by Philpott, left the relationship.
Mr Orchard said: “In relation to the children, you would agree that he was a good father?”
“Yes, he was a good father,” Miss Willis said. He took them to school, played football with them, took some of them fishing, and he did not let them play in the street because he cared about their safety. He asked Miss Willis: “He would do nothing to endanger them?”
“No,” she replied.
Earlier, Miss Willis told the jury she had met Philpott when she was around 17 and moved in with him and Mairead at their council home in Victory Road.
Miss Willis said when the Philpotts decided to marry she was a bridesmaid at their wedding and she and Mrs Philpott were good friends. She treated their children as her own, she said, and they regularly shared childcare responsibilities.
Asked how she felt when she found out the six Philpott children had died in the house fire she said: “I was devastated.”
Her relationship with Philpott became sexual shortly after she moved in, something she claimed Mrs Philpott was not upset by and the three embarked upon an unconventional life together.
“We took it in turns, we never had all three of us together,” she said. “We would take it in turns at night so one night it would be me, one night it would be Mairead.”
Her relationship with Philpott was not an easy one, she said, and was peppered with violence and his controlling behaviour – her wages and her benefits went into his bank account – and his demands to know where she was going, who with, and accusations of affairs left her reluctant to leave the house. She also did not have her own key to the family home.
In one incident Philpott repeatedly hit her on the legs, back and arms with a piece of wood.
Miss Willis left on February 11 last year, having said she was taking the children swimming.
At the beginning of May she received a call from the police in relation to threats she was alleged to have made against Philpott.
Mr Latham asked her: “Have you ever made any threats to him or his family?” Miss Willis replied: “No, none whatsoever.”
The prosecutor asked Miss Willis where she was on the night of the fire. She told the court her sister and children were at her house until 8pm on May 10 and she never went near 10 Victory Road that night or discussed it with he4r sister.
The trial continues today.